[PATCH 2/2 v2] tty/serial/8250: use mctrl_gpio helpers

Stefan Roese
2019-05-24T09:48:41Z

From: Yegor Yefremov <yegorslists@googlemail.com>

This patch permits the usage for GPIOs to control
the CTS/RTS/DTR/DSR/DCD/RI signals.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Giulio Benetti <giulio.benetti@micronovasrl.com>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
v2:
- No change

Please note that this patch was already applied before [1]. And later
reverted [2] because it introduced problems on some x86 based boards
(ACPI GPIO related). Here a detailed description of the issue at that
time:

https://lkml.org/lkml/2016/8/9/357
http://www.spinics.net/lists/linux-serial/msg23071.html

This is a re-send of the original patch that was applied at that time.
With patch 1/2 from this series this issue should be fixed now (please
note that I can't test it on such an x86 platform causing these
problems).

Andy (or Mika), perhaps it would be possible for you to test this
patch again, now with patch 1/2 of this series applied as well?
That would be really helpful.

Thanks,
Stefan

[1] 4ef03d328769 ("tty/serial/8250: use mctrl_gpio helpers")
[2] 5db4f7f80d16 ("Revert "tty/serial/8250: use mctrl_gpio helpers"")

.../devicetree/bindings/serial/8250.txt | 19 ++++++++++
drivers/tty/serial/8250/8250.h | 35 ++++++++++++++++++-
drivers/tty/serial/8250/8250_core.c | 9 +++++
drivers/tty/serial/8250/8250_omap.c | 31 +++++++++-------
drivers/tty/serial/8250/8250_port.c | 7 +++-
drivers/tty/serial/8250/Kconfig | 1 +
include/linux/serial_8250.h | 1 +
7 files changed, 88 insertions(+), 15 deletions(-)

diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
index 3cba12f855b7..20d351f268ef 100644
--- a/Documentation/devicetree/bindings/serial/8250.txt
+++ b/Documentation/devicetree/bindings/serial/8250.txt
@@ -53,6 +53,9 @@ Optional properties:
programmable TX FIFO thresholds.
- resets : phandle + reset specifier pairs
- overrun-throttle-ms : how long to pause uart rx when input overrun is encountered.
+- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
+ line respectively. It will use specified GPIO instead of the peripheral
+ function pin for the UART feature. If unsure, don't specify this property.

Note:
* fsl,ns16550:
@@ -74,3 +77,19 @@ Example:
interrupts = <10>;
reg-shift = <2>;
};
+
+Example for OMAP UART using GPIO-based modem control signals:
+
+ uart4: serial@49042000 {
+ compatible = "ti,omap3-uart";
+ reg = <0x49042000 0x400>;
+ interrupts = <80>;
+ ti,hwmods = "uart4";
+ clock-frequency = <48000000>;
+ cts-gpios = <&gpio3 5 GPIO_ACTIVE_LOW>;
+ rts-gpios = <&gpio3 6 GPIO_ACTIVE_LOW>;
+ dtr-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>;
+ dsr-gpios = <&gpio1 13 GPIO_ACTIVE_LOW>;
+ dcd-gpios = <&gpio1 14 GPIO_ACTIVE_LOW>;
+ rng-gpios = <&gpio1 15 GPIO_ACTIVE_LOW>;
+ };
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index ebfb0bd5bef5..e59625bdb007 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -11,6 +11,8 @@
#include <linux/serial_reg.h>
#include <linux/dmaengine.h>

+#include "../serial_mctrl_gpio.h"
+
struct uart_8250_dma {
int (*tx_dma)(struct uart_8250_port *p);
int (*rx_dma)(struct uart_8250_port *p);
@@ -141,12 +143,43 @@ void serial8250_em485_destroy(struct uart_8250_port *p);

static inline void serial8250_out_MCR(struct uart_8250_port *up, int value)
{
+ int mctrl_gpio = 0;
+
serial_out(up, UART_MCR, value);
+
+ if (value & UART_MCR_RTS)
+ mctrl_gpio |= TIOCM_RTS;
+ if (value & UART_MCR_DTR)
+ mctrl_gpio |= TIOCM_DTR;
+
+ mctrl_gpio_set(up->gpios, mctrl_gpio);
}

static inline int serial8250_in_MCR(struct uart_8250_port *up)
{
- return serial_in(up, UART_MCR);
+ int mctrl, mctrl_gpio = 0;
+
+ mctrl = serial_in(up, UART_MCR);
+
+ /* save current MCR values */
+ if (mctrl & UART_MCR_RTS)
+ mctrl_gpio |= TIOCM_RTS;
+ if (mctrl & UART_MCR_DTR)
+ mctrl_gpio |= TIOCM_DTR;
+
+ mctrl_gpio = mctrl_gpio_get_outputs(up->gpios, &mctrl_gpio);
+
+ if (mctrl_gpio & TIOCM_RTS)
+ mctrl |= UART_MCR_RTS;
+ else
+ mctrl &= ~UART_MCR_RTS;
+
+ if (mctrl_gpio & TIOCM_DTR)
+ mctrl |= UART_MCR_DTR;
+ else
+ mctrl &= ~UART_MCR_DTR;
+
+ return mctrl;
}

#if defined(__alpha__) && !defined(CONFIG_PCI)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index e441221e04b9..ec0c5448c192 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -982,6 +982,8 @@ int serial8250_register_8250_port(struct uart_8250_port *up)

uart = serial8250_find_match_or_unused(&up->port);
if (uart && uart->port.type != PORT_8250_CIR) {
+ struct mctrl_gpios *gpios;
+
if (uart->port.dev)
uart_remove_one_port(&serial8250_reg, &uart->port);

@@ -1016,6 +1018,13 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
if (up->port.flags & UPF_FIXED_TYPE)
uart->port.type = up->port.type;

+ gpios = mctrl_gpio_init(&uart->port, 0);
+ if (IS_ERR(gpios)) {
+ if (PTR_ERR(gpios) != -ENOSYS)
+ return PTR_ERR(gpios);
+ } else
+ uart->gpios = gpios;
+
serial8250_set_defaults(uart);

/* Possibly override default I/O functions. */
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 0a8316632d75..562ac73d9f2f 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -141,18 +141,21 @@ static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)

serial8250_do_set_mctrl(port, mctrl);

- /*
- * Turn off autoRTS if RTS is lowered and restore autoRTS setting
- * if RTS is raised
- */
- lcr = serial_in(up, UART_LCR);
- serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
- if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
- priv->efr |= UART_EFR_RTS;
- else
- priv->efr &= ~UART_EFR_RTS;
- serial_out(up, UART_EFR, priv->efr);
- serial_out(up, UART_LCR, lcr);
+ if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(up->gpios,
+ UART_GPIO_RTS))) {
+ /*
+ * Turn off autoRTS if RTS is lowered and restore autoRTS
+ * setting if RTS is raised
+ */
+ lcr = serial_in(up, UART_LCR);
+ serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+ if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
+ priv->efr |= UART_EFR_RTS;
+ else
+ priv->efr &= ~UART_EFR_RTS;
+ serial_out(up, UART_EFR, priv->efr);
+ serial_out(up, UART_LCR, lcr);
+ }
}

/*
@@ -453,7 +456,9 @@ static void omap_8250_set_termios(struct uart_port *port,
priv->efr = 0;
up->port.status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS | UPSTAT_AUTOXOFF);

- if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW) {
+ if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW
+ && IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(up->gpios,
+ UART_GPIO_RTS))) {
/* Enable AUTOCTS (autoRTS is enabled when RTS is raised) */
up->port.status |= UPSTAT_AUTOCTS | UPSTAT_AUTORTS;
priv->efr |= UART_EFR_CTS;
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 2304a84eee3b..220a78287d88 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1662,6 +1662,8 @@ static void serial8250_disable_ms(struct uart_port *port)
if (up->bugs & UART_BUG_NOMSR)
return;

+ mctrl_gpio_disable_ms(up->gpios);
+
up->ier &= ~UART_IER_MSI;
serial_port_out(port, UART_IER, up->ier);
}
@@ -1674,6 +1676,8 @@ static void serial8250_enable_ms(struct uart_port *port)
if (up->bugs & UART_BUG_NOMSR)
return;

+ mctrl_gpio_enable_ms(up->gpios);
+
up->ier |= UART_IER_MSI;

serial8250_rpm_get(up);
@@ -1959,7 +1963,8 @@ unsigned int serial8250_do_get_mctrl(struct uart_port *port)
ret |= TIOCM_DSR;
if (status & UART_MSR_CTS)
ret |= TIOCM_CTS;
- return ret;
+
+ return mctrl_gpio_get(up->gpios, &ret);
}
EXPORT_SYMBOL_GPL(serial8250_do_get_mctrl);

diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 296115f6a4d8..509f6a3bb9ff 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -8,6 +8,7 @@ config SERIAL_8250
tristate "8250/16550 and compatible serial support"
depends on !S390
select SERIAL_CORE
+ select SERIAL_MCTRL_GPIO if GPIOLIB
---help---
This selects whether you want to include the driver for the standard
serial ports. The standard answer is Y. People who might say N
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index 5a655ba8d273..14cd763baf78 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -114,6 +114,7 @@ struct uart_8250_port {
* if no_console_suspend
*/
unsigned char probe;
+ struct mctrl_gpios *gpios;
#define UART_PROBE_RSA (1 << 0)

/*
--
2.21.0